Untreated celiac disease commonly produces multiple nutrient shortages because immune-mediated damage to the small intestinal lining impairs absorption. Clinically important deficits include iron deficiency, folate deficiency, vitamin B12 deficiency, vitamin D deficiency, calcium deficiency, and deficits of zinc, magnesium, and vitamin K. These problems are well described in clinical reviews and guidelines and are emphasized by experts such as Alessio Fasano Massachusetts General Hospital and Harvard Medical School and by clinical authorities at the National Institute of Diabetes and Digestive and Kidney Diseases.
Causes of deficiencies
The primary mechanism is villous atrophy and inflammation of the small intestinal mucosa, especially the proximal small bowel where iron and folate are absorbed. This explains why iron and folate deficiencies are particularly frequent in untreated disease. Vitamin B12 is absorbed in the ileum and is less commonly deficient solely from celiac-related damage, but it can occur when extensive disease, bacterial overgrowth, or concomitant conditions exist. Malabsorption of fat-soluble vitamins, notably vitamin D, arises when mucosal function and fat digestion are impaired, contributing to poor calcium uptake and altered bone metabolism. Expert clinicians including Joseph A. Murray Mayo Clinic highlight malabsorption as the central pathophysiologic driver for these deficits.
Consequences and clinical context
Nutritional deficits carry clear clinical consequences: iron deficiency and folate deficiency lead to microcytic and megaloblastic anemia respectively, vitamin D and calcium insufficiency increase the risk of osteopenia and osteoporosis, and deficiencies of zinc and magnesium can impair wound healing, immune function, and neuromuscular stability. Neurologic symptoms such as neuropathy may follow long-standing B12 or vitamin E lack, while children can show growth failure and delayed puberty. The National Institute of Diabetes and Digestive and Kidney Diseases advises that evaluation for these deficiencies be part of the workup for suspected or newly diagnosed celiac disease.
Cultural and territorial factors influence presentation and outcomes. In regions without flour fortification, folate shortfalls may be worse. Limited access to affordable, certified gluten-free foods can prolong exposure to gluten and perpetuate malabsorption. Diagnosis and management by a knowledgeable clinician and targeted laboratory testing guide appropriate supplementation and dietary treatment to reduce long-term complications.